We have recently had a new (and much more powerful) heating system installed in our Victorian sandstone home and have noticed a sudden build up of salt crystals on an exterior wall. Historically this had been an issue (long before we moved in 18 months ago looking at the wall) but to nowhere near the same extent and seems to have been amplified by our home being much warmer compared with outside that it previously has even been.
Externally the buildup occurs in 2 places. The conditions on the internal side of the wall are as follows:
(1) the salt follows the line of the stairs down into the cellar - internally there is a wooden board fixed to the wall at the point where the salt begins (below the line it is just painted stone as in the rest of the cellar).
(2) the second salt area is on the other side of the wall to our kitchen cupboards. Similarly these are fixed internally to some sort of board.
I suspect that the moisture is being trapped behind the walls internally due to the boards and then forced out through the stone.
I would very much appreciate any opinions on how to mitigate the issue, and prevent future buildup!
Cheers